A dc-dc converter is disclosed comprising an active clamp topology, including an active clamp resonant transition system to provide substantially zero or reduced voltage for turn-on of the primary switch. The resonant transition system includes an inductor in series with the primary winding of the power transformer and a clamp diode that operate cooperatively to turn on the primary switch with reduced voltage. A second diode is included in series with a balancing resistor to discharge a snubber capacitor with improved efficiency. The addition of these circuit components provides low switching losses and low component stresses in the overall design.
Legal claims defining the scope of protection, as filed with the USPTO.
1. An active clamp power converter, comprising: a power transformer with a primary winding; a primary switch coupling the primary winding of the power transformer to an input power source; a reset switch coupled to a clamp capacitor and to the primary winding of the power transformer; an inductor coupled between the primary winding of the power transformer and the primary switch; and a first diode coupled between the inductor and the clamp capacitor.
2. The active clamp power converter as recited in claim 1 , further comprising a second diode coupled between the inductor and ground.
3. The active clamp resonant transition system as recited in claim 1 , further comprising a brief delay between turn-off of the reset switch and turn-on of the primary switch.
4. The active clamp resonant transition system as recited in claim 1 , further comprising a brief delay between turn-off of the primary switch and turn-on of the reset switch.
5. An active clamp power converter, comprising: a power transformer with a primary winding; a primary switch coupling the primary winding of a power transformer to an input power source; a reset switch coupled to a clamp capacitor and the primary winding of the power transformer; an inductor coupled between the primary winding of the power transformer and the primary switch; and a series circuit arrangement of a first diode and a snubber capacitor coupled to the inductor and to the primary winding of the power transformer.
6. The active clamp resonant transition system as recited in claim 5 , further comprising a second diode coupled between the inductor and ground.
7. The active clamp resonant transition system as recited in claim 5 , further comprising a circuit element coupled between the clamp capacitor and the snubber capacitor.
8. The active clamp resonant transition system as recited in claim 7 , further comprising a third diode coupled in series with the circuit element.
9. The active clamp resonant transition system as recited in claim 7 , wherein the circuit element is a resistor.
10. The active clamp resonant transition system as recited in claim 5 , further comprising a brief delay between turn-off of the reset switch and turn-on of the primary switch.
11. The active clamp resonant transition system as recited in claim 5 , further comprising a brief delay between turn-off of the primary switch and turn-on of the reset switch.
12. A method of reducing switch turn-on voltage in an active clamp power converter having a power transformer with a primary winding, comprising: coupling the primary winding of the power transformer to an input power source with a primary switch; coupling a reset switch to a clamp capacitor and to the primary winding of the power transformer; coupling an inductor between the primary winding of the power transformer and the primary switch; coupling a series circuit arrangement of a first diode and a snubber capacitor to the inductor and to the primary winding of the power transformer; and coupling a circuit element between the clamp capacitor and the snubber capacitor.
13. The method as recited in claim 12 , further comprising coupling a second diode between the inductor and ground.
14. The method as recited in claim 12 , further comprising coupling a circuit element between the clamp capacitor and the snubber capacitor.
15. The method as recited in claim 14 , further comprising coupling a third diode in series with the circuit element.
16. The method as recited in claim 14 , wherein the circuit element is a resistor.
17. The method as recited in claim 12 , further comprising providing a brief delay between turn-off of the reset switch and turn-on of the primary switch.
18. The method as recited in claim 12 , further comprising providing a brief delay between turn-off of the primary switch and turn-on of the reset switch.
Cooperative Patent Classification codes for this invention. Click any code to explore related patents in that topic.
April 29, 2005
August 15, 2006
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